(a) Field of the Invention
The present invention relates to a display device and a method for manufacturing the same, and more particularly, to a display device comprising an organic thin film transistor and a method for manufacturing the same.
(b) Description of the Related Art
Recently, flat panel display devices having the dual advantages of smaller size and lighter weight have received increasing attention in the marketplace. Such a flat display device typically comprises a liquid crystal display (LCD) and an organic light emitting diode (OLED). In general, the liquid crystal display device comprises a thin film transistor substrate on which a thin film transistor is provided, a color filter substrate on which a color filter is provided and a liquid crystal layer interposed between both substrates.
In this case, the thin film transistor substrate is the switching and driving element for controlling the operation of each pixel where each thin film transistor comprises a gate electrode, a source electrode and a drain electrode spaced from each other with the gate electrode as a center to define a channel region and a semiconductor layer. Amorphous silicon or poly silicon typically forms the semiconductor layer. According to a recent study related to applying an organic semiconductor to the semiconductor layer, the organic semiconductor can be formed at a normal temperature and pressure, and so that the manufacturing costs may be reduced and the organic semiconductor layer can be formed on a plastic substrate which is vulnerable to heat.
However, a work function of organic semiconductor is larger than that of aluminum, chrome, molybdenum or the like used as the source and drain electrodes, and so a characteristic of the organic thin film transistor is undesirable. Accordingly, instead of the above metals, transparent electrode material such as indium tin oxide (ITO) or indium zinc oxide (IZO) having a work function which is similar to or larger than that of organic semiconductor is used for forming the source electrode and the drain electrode. However, ITO or IZO is disadvantageous in that a resistance of ITO or IZO is large so that the electrode made of ITO or IZO is not suited to the data wires. In order to solve the above problem, an organic thin film transistor having a buried data wire structure in which data wires made of metal with a low resistance are provided at a lower side, a source electrode and a drain electrode is made of indium tin oxide or indium zinc oxide and data wires are connected to the source and drain electrodes has been developed and manufactured.
However, the above mentioned buried data wire structure is not effective in that a manufacturing process is complicated, and a great number of masks are required for carrying out the manufacturing process so that manufacturing cost is increased.